The present invention relates to a method for analyzing a gas mixture which contains a dust-like solid, by separating and directing to analysis a certain quantity of the gas mixture along a conduit for sample-taking, a method wherein a known quantity of liquid is mixed with the separated gas mixture in order to absorb the gas mixture into the liquid, and the analysis is performed by analyzing the liquid which has absorbed the gas mixture.
It is previously known to measure the dust content of flue gases by taking a sample from the flue gases at suitable intervals and by analyzing the dust content of this sample.
It is also known to measure the dust content of flue gases continuously by photo-optics, which , however, yields data which only approximately indicate the change in the dust amount.
From German Patent Application No. 27 23 310 there is, furthermore, known a method and apparatus for continuous analysis of gas by absorbing gas into a flowing liquid and by measuring by means of an ion-sensitive electrode the ions absorbed from the gas into the liquid, wherein the absorption liquid is mixed in the form of a fine mist with the gas just before the measuring, the liquid phase is separated from the gas and directed as a continuous flow through a measuring vessel equipped with an ion-specific electrode.
However, it is not possible to analyze dust-bearing gases by means of this prior known method and apparatus. In the apparatus the sample gas must travel dry over the entire length of the sample-taking pipe to the absorption point; in practice this would be a distance of several meters. In such a situation, during the measuring any dust will accumulate on the walls of the conduit, from which it must, when the quantity and components of the dust are being measured, be washed into the sample for analysis, in which case it will cause flow disturbances in the sample taking, for example, preventing the realization of the isokinetic nature of the sample taking.
In the method in the publication, the absorption takes place in a liquid spray, in which case the retention of the sample gas in the absorption is quite short and the absorption surface area is quite small, and the absorption is thus carried out very incompletely. In this case it is not possible to measure the quantitative values of the substances, and it is necessary to settle for only an indication whether or not some substance is possibly present in the gas mixture being measured. Furthermore, gases present in very low concentrations and gases which are absorbed poorly remain undetected, since owing to the short absorption time they do not have time to be absorbed in observable concentrations into the liquid.
The object of the present invention is to provide a method by which it is possible, even continuously, to measure both qualitatively and quantitatively the constituents of a gas mixture which contains a possibly dust-containing solid, and in particular a method for continuous measuring of the concentration of glauber salt in the flue gases from a recovery boiler.
In the description and claims of this Application, by the analysis of a gas mixture which contains a possibly dust-containing solid is meant the analysis of the gaseous constituents of the gas mixture and/or its various solid constituents which are in a dust-like form. By the gas mixture, respectively, is meant a combination which contains at minimum two gaseous substances or at minimum one gaseous substance and at minimum one solid.